One challenge facing research on categories is to explain their content and the extent to which they gain meaning from cultural material that originates from moral arenas. This article suggests that categories are an outcome of strategic framing activities by which market members draw on prevalent master frames as cultural material to infuse an emerging market with meaning. It depicts the construction of a market category that emerges at the boundary between the economic sphere of a market and the moral sphere of social movements. A qualitative study of the use of movement master frames in categorizing the market for ethical fashion in the United Kingdom indicates the important role of movements' cultural legacy for the categorization of a moral market. It shows that the master frame of the environmental movement prevails in market categorization. Furthermore, we see that market members tend to adopt movement frames in categorization to discuss solutions rather than to talk about problems. Two propositions are drawn from these findings. First, when market making happens at the boundary of several social movements, market members adopt the master frame mainly of the movement whose activism has already led to changes in the political agenda, in social beliefs and practices in society. Second, framing tactics change when movement frames leave the moral sphere of activist mobilization and enter the economic sphere. While talking about problems has been shown to be as important as the provision of solutions in the movement arena, providing solutions becomes more important when movement frames are adopted in the economic arena of a market.